Methods for small trench patterning using chemical amplified photoresist compositions

ABSTRACT

A method for forming a pattern on a substrate is described. The method includes providing a substrate, forming a photosensitive layer over the substrate, exposing the photosensitive layer to a first exposure energy through a first mask, exposing the photosensitive layer to a second exposure energy through a second mask, baking the photosensitive layer, and developing the exposed photosensitive layer. The photosensitive layer includes a polymer that turns soluble to a developer solution, at least one photo-acid generator (PAG), and at least one photo-base generator (PBG). A portion of the layer exposed to the second exposure energy overlaps with a portion exposed to the first exposure energy.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs where each generation has smaller and more complexcircuits than the previous generation. In the course of IC evolution,functional density (i.e., the number of interconnected devices per chiparea) has generally increased while geometry size (i.e., the smallestcomponent (or line) that can be created using a fabrication process) hasdecreased. This scaling down process generally provides benefits byincreasing production efficiency and lowering associated costs. Suchscaling down has also increased the complexity of processing andmanufacturing ICs and, for these advances to be realized, similardevelopments in IC processing and manufacturing are needed. For example,conventional photoresist or photosensitive layers comprise a base, whichis not photosensitive. Thus, after an exposure process, exposed areas ofa photoresist layer may exhibit less than desirable acid distributioncontrast and base distribution contrast. This leads to lower patterncontrast, resulting in poor pattern profiles and/or poor resolution,particularly as pattern features continue to decrease in size.

Old methods for forming small trench critical dimensions (CDs) and smalltrench end-to-end spaces usually require a high cost exposure tool, suchas EUV. Pattern shrinkage, which often trades off trench CDs forend-to-end CDs, also remains a problem.

Accordingly, what is needed is a method and photoresist material formanufacturing an integrated circuit device that addresses the abovestated issues.

SUMMARY

The present disclosure relates to a method for forming a pattern on asubstrate. The method includes providing a substrate, forming aphotosensitive layer over the substrate, exposing the photosensitivelayer to a first exposure energy through a first mask, exposing thephotosensitive layer to a second exposure energy through a second mask,baking the photosensitive layer, and developing the exposedphotosensitive layer. The photosensitive layer includes a polymer thatturns soluble to a developer solution, at least one photo-acid generator(PAG), and at least one photo-base generator (PBG). A portion of thelayer exposed to the second exposure energy overlaps with a portionexposed to the first exposure energy.

In another embodiment, the method for forming a pattern on a substratethat includes providing a substrate forming a photosensitive layer on asubstrate, exposing the photosensitive layer to the first exposureenergy through a first mask, exposing the photosensitive layer to thesecond exposure energy through a second mask, baking the photosensitivelayer, and developing the exposed photosensitive layer. Thephotosensitive layer includes a polymer that turns soluble to adeveloper solution, a PAG at a first concentration that decomposes toform acid in response to a first exposure energy, and a PBG at a secondconcentration that decomposes to form a base in response to a secondexposure energy. A portion of the layer exposed to the second exposureenergy overlaps with a portion exposed to the first exposure energy.

In yet another embodiment, the method for forming a pattern on asubstrate includes providing a substrate, forming a photosensitive layeron a substrate, wherein the photosensitive layer comprising a polymerthat turns soluble to a developer solution, PAG at a first concentrationthat decomposes to form acid in response to a first exposure energy, andPBG at a second concentration that decomposes to form a base in responseto a second exposure energy, adjusting the first concentration, secondconcentration, or both to improve contrast and/or a critical dimensionin the pattern, adjusting an intensity of the first exposure energy,second exposure energy, or both to improve contrast and/or a criticaldimension in the pattern, exposing the photosensitive layer to the firstexposure energy through a first mask, exposing the photosensitive layerto the second exposure energy through a second mask, baking thephotosensitive layer, and developing the exposed photosensitive layer. Aportion of the layer exposed to the second exposure energy overlaps withthe a portion exposed to the first exposure energy.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a flowchart of a method for forming a pattern on a substrateconstructed according to aspects of the present disclosure.

FIG. 2. illustrate sectional views of semiconductor device having aphotosensitive layer at various stages of a lithography processconstructed according to aspects of the present disclosure in anembodiment.

FIG. 3 illustrates a method for forming a pattern on a substrateconstructed according to aspects of the present disclosure in anembodiment.

FIG. 4 illustrates the intensity and position for the first exposure ina method for forming a pattern on a substrate constructed according toaspects of the present disclosure in an embodiment.

FIG. 5 illustrates the intensity and position for the second exposure ina method for forming a pattern on a substrate constructed according toaspects of the present disclosure in an embodiment.

FIG. 6 illustrates the cumulative exposure energy resulting from thefirst and second exposures in FIGS. 4 and 5.

FIG. 7 illustrates the comparison between an original single exposurewith the double exposure of FIG. 6.

FIG. 8 illustrates a pattern design in a method for forming a pattern ona substrate constructed according to aspects of the present disclosurein an embodiment.

FIG. 9 illustrates a pattern design in a method for forming a pattern ona substrate constructed according to aspects of the present disclosurein an embodiment

DETAILED DESCRIPTION

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of variousembodiments. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Forexample, the formation of a first feature over or on a second feature inthe description that follows may include embodiments in which the firstand second features are formed in direct contact, and may also includeembodiments in which additional features may be formed interposing thefirst and second features, such that the first and second features maynot be in direct contact. In addition, the present disclosure may repeatreference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

The method 100 is a lithography method for use in manufacturing asemiconductor device. The terms lithography, immersion lithography,photolithography, and optical lithography may be used interchangeably inthe present disclosure. Photolithography is a process used inmicrofabrication, such as semiconductor fabrication, to selectivelyremove parts of a thin film or a substrate. The process uses light totransfer a pattern (e.g., a geometric pattern) from a photomask to alight-sensitive layer (e.g., photoresist, or simply “resist”) on thesubstrate. The light causes a chemical change in exposed regions of thelight-sensitive layer, which may increase or decrease solubility of theexposed regions. If the exposed regions become more soluble, thelight-sensitive layer is referred to as a positive photoresist. If theexposed regions become less soluble, the light-sensitive layer isreferred to as a negative photoresist. Baking processes may be performedbefore or after exposing the substrate, such as a post-exposure bakingprocess. A developing process selectively removes the exposed orunexposed regions with a developing solution creating an exposurepattern over the substrate. A series of chemical treatments may thenengrave/etch the exposure pattern into the substrate (or materiallayer), while the patterned photoresist protects regions of theunderlying substrate (or material layer). Alternatively, metaldeposition, ion implantation, or other processes can be carried out.Finally, an appropriate reagent removes (or strips) the remainingphotoresist, and the substrate is ready for the whole process to berepeated for the next stage of circuit fabrication. In a complexintegrated circuit (for example, a modern CMOS), a substrate may gothrough the photolithographic cycle a number of times.

Referring to FIG. 1, the method 100 begins at block 102 by providing asubstrate 210. The semiconductor device 200 and the method of making thesame are collectively described. The semiconductor device 200 may be asemiconductor wafer or other suitable device. In the present embodiment,the semiconductor device 200 includes a silicon substrate 210 havingvarious doped regions, dielectric features, and/or multilevelinterconnects. The substrate 210 may alternatively include othersuitable semiconductor material, including Ge, SiGe, or GaAs. Thesubstrate may alternatively include a non-semiconductor material such asa glass plate for thin-film-transistor liquid crystal display (TFT-LCD)devices. The semiconductor device 200 may further include one or morematerial layers to be patterned. Additionally, disposed on thesemiconductor substrate 210 are other suitable material layers includingorganic bottom anti reflecting coating (BARC), inorganic BARC, etchresistance organic layer, and/or adhesion enhancement organic layer.

The substrate 210 includes various doped regions depending on designrequirements as known in the art (e.g., p-type wells or n-type wells).The doped regions are doped with p-type dopants, such as boron or BF₂;n-type dopants, such as phosphorus or arsenic; or combinations thereof.The doped regions may be formed directly on the substrate 210, in aP-well structure, in a N-well structure, in a dual-well structure, orusing a raised structure. The semiconductor substrate 210 may furtherinclude various active regions, such as regions configured for an N-typemetal-oxide-semiconductor transistor device (referred to as an NMOSdevice) and regions configured for a P-type metal-oxide-semiconductortransistor device (referred to as a PMOS device). It is understood thatthe semiconductor device 200 may be formed by CMOS technologyprocessing, and thus some processes are not described in detail herein.

The method 100 proceeds to step 104, where a photosensitive layercontaining a polymer, PAG, and PBG is formed. FIG. 2 provides sectionalviews of a semiconductor device 200 at various lithography patterningsteps. Referring to FIG. 2, a photosensitive material layer (orphotosensitive layer, photoresist layer or resist layer) 220 is disposedon the substrate 210. For example, a spin-coating technique is utilizedto form the photosensitive layer 220 on the substrate 210. Thephotoresist layer is a positive-type or negative-type resist materialand may have a multi-layer structure. The photosensitive layer 220utilizes a chemical amplification (CA) resist material. In oneembodiment, a positive CA resist material includes a polymer materialthat turns soluble to a developer such as a base solution after thepolymer is reacted with acid. Alternatively, the CA resist material canbe negative and include a polymer material that turns insoluble to adeveloper such as a base solution after the polymer is reacted withacid. The photosensitive layer 220 further includes a solvent fillinginside the polymer. The solvent may be partially evaporated by a softbaking process. The photosensitive layer 220 also includes photo-acidgenerator (PAG) distributed in the photosensitive layer 220. Whenabsorbing photo energy, the PAG decomposes and forms a small amount ofacid 222. The PAG may have any suitable concentration, as is known inthe art. After post exposure baking (PEB) and developing by a basicsolution, an opening or trench 224 is revealed. Typically, the contrastat the edges of the trench 224 is blurred and results in errors in theCDs of the trench because the exposure energy decreases near the edges.

Examples of the PAG, that is, a compound capable of generating an acidupon exposure to high energy exposure are given below. It should beunderstood that they may be used alone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates.Exemplary sulfonium cations include triphenylsulfonium,(4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium, (3-tert-butoxyphenyl)diphenylsulfonium, bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxypheny-1)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyldimethylsulfonium, trimethylsulfonium,diphenylmethylsulfonium, methyl-2-oxopropylphenylsulfonium,2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium, andtribenzylsulfonium. Exemplary sulfonates includetrifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, and methanesulfonate.

Iodinium salts are salts of iodonium cations with sulfonates. Exemplaryiodinium cations are aryliodonium cations including diphenyliodinium,bis(4-tert-butylphenyl)iodonium, 4-tert-butoxyphenylphenyliodonium, and4-methoxyphenylphenyliodonium. Exemplary sulfonates includetrifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, and methanesulfonate. Iodoniumsalts based on combination of the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonylcarbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazo-methane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyl-diazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide PAGs include combinations of imide skeletons withsulfonates. Exemplary imide skeletons are succinimide, naphthalenedicarboxylic acid imide, phthalimide, cyclohexylcarboxylic acid imide,5-norbornene-2,3-dicarboxylic acid imide, and7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide. Exemplarysulfonates include trifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, and methanesulfonate.

Benzoinsulfonate PAGs include benzoin tosylate, benzoin mesylate, andbenzoin butanesulfonate.

Pyrogallol trisulfonate PAGs include pyrogallol, fluoroglycine,catechol, resorcinol, and hydroquinone, in which all the hydroxyl groupsare replaced by trifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, and methanesulfonate.

Nitrobenzyl sulfonate PAGs include 2,4-dinitrobenzyl sulfonate,2-nitrobenzyl sulfonate, and 2,6-dinitrobenzyl sulfonate, with exemplarysulfonates including trifluoromethanesulfonate,nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,toluenesulfonate, benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate. Also useful are analogousnitrobenzyl sulfonate compounds in which the nitro group on the benzylside is replaced by a trifluoromethyl group.

Sulfone PAGs include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

PAGs in the form of glyoxime derivatives includebis-o-(p-toluenesulfonyl)-.alpha.-dimethylglyoxime,bis-o-(p-toluenesulfonyl)-.alpha.-diphenylglyoxime,bis-o-(p-toluenesulfonyl)-.alpha.-dicyclohexylglyoxime,bis-o-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-o-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-.alpha.-dimethylglyoxime,bis-o-(n-butanesulfonyl)-.alpha.-diphenylglyoxime,bis-o-(n-butanesulfonyl)-.alpha.-dicyclohexylglyoxime,bis-o-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(methanesulfonyl)-.alpha.-dimethylglyoxime,bis-o-(trifluoromethane-sulfonyl)-.alpha.-dimethylglyoxime,bis-o-(1,1,1-trifluoroethanesulfonyl)--.alpha.-dimethylglyoxime,bis-o-(tert-butanesulfonyl)-.alpha.-dimethylglyoxime,bis-o-(perfluorooctanesulfonyl)-.alpha.-dimethylglyoxime,bis-o-(cyclohexylsulfonyl)-.alpha.-dimethylglyoxime,bis-o-(benzenesulfonyl)-.alpha.-dimethylglyoxime,bis-o-(p-fluorobenzenesulfonyl)-.alpha.-dimethylglyoxime,bis-o-(p-tert-butylbenzenesulfonyl)-.alpha.-dimethylglyoxime,bis-o-(xylenesulfonyl)-.alpha.-dimethylglyoxime, andbis-o-(camphorsulfonyl)-.alpha.-dimethylglyoxime.

The photosensitive layer 220 also includes a photo-base generator (PBG)(not shown) distributed in the polymer. When absorbing photo energy, thePBG decomposes and forms a small amount of base. The PBG may have anysuitable concentration, as is known in the art. The PBG is capable ofneutralizing acid, and specifically the acid formed by the activation ofthe PAG. The PBG tightens resolution to provide improved patterns,increased contrast, and smaller CDs for the trench 224. The resolutionof resulting patterns is improved by, for example, tuning or adjustingthe loading or concentration of the PBGs with respect to the PAGs. Forexample, the ratios of the PAG to the PBG may be optimized such that theconcentration of PBG in the photosensitive layer 220 is greater than theconcentration of the PAG, e.g., the ratio of PAG to PBG may be 1:1.2,1:1.4, 1:1.6, 1:2, etc. Alternatively, the PAG and PBG may be present insimilar amounts.

Examples of the PBG include at least one of a carbamate, acarbamonylhydroxyamine, oxime, sulfonamide, lactam (or cyclic amide),other suitable materials, and/or combinations thereof. An exemplarycarbamate is represented by the formula:

R1, R2, R3, R4, and/or R5 comprise a hydrogen, a hydroxide (OH), ahalide, an aromatic carbon ring, a straight or cyclic alkyl chain, astraight or cyclic alkoxyl chain, a straight or cyclic fluoroalkylchain, a straight or cyclic fluoroalkoxyl chain, other suitablematerial, and/or combinations thereof. A chain contains from about 1 toabout 8 carbon atoms. The straight or cyclic alkyl, alkoxyl,fluoroalkyl, and/or fluoroalkoxyl chain can comprise a hydroxide (—OH),an amine, a sulfhydryl (thiol) (—SH), a lactone, an amide, a carboxylicacid, and/or ester functional group. It is understood that the straightor cyclic alkyl, alkoxyl, fluoroalkyl, and/or fluoroalkoxyl chain maycomprise other suitable functional groups.

An exemplary carbamonylhydroxyamine is represented by the formula:

R6, R7, R8, R9, and/or R10 comprise a hydrogen, a hydroxide (OH), ahalide, an aromatic carbon ring, a straight or cyclic alkyl chain, astraight or cyclic alkoxyl chain, a straight or cyclic fluoroalkylchain, a straight or cyclic fluoroalkoxyl chain, other suitablematerial, and/or combinations thereof. A chain contains from about 1 toabout 8 carbon atoms. The straight or cyclic alkyl, alkoxyl,fluoroalkyl, and/or fluoroalkoxyl chain can comprise a hydroxide (—OH),an amine, a sulfhydryl (thiol) (—SH), a lactone, an amide, a carboxylicacid, and/or ester functional group. It is understood that the straightor cyclic alkyl, alkoxyl, fluoroalkyl, and/or fluoroalkoxyl chain maycomprise other suitable functional groups.

An exemplary oxime is represented by the formula:

R11, R12, and/or R13 comprise a hydrogen, a hydroxide (OH), a halide, anaromatic carbon ring, a straight or cyclic alkyl chain, a straight orcyclic alkoxyl chain, a straight or cyclic fluoroalkyl chain, a straightor cyclic fluoroalkoxyl chain, other suitable material, and/orcombinations thereof. A chain contains from about 1 to about 8 carbonatoms. The straight or cyclic alkyl, alkoxyl, fluoroalkyl, and/orfluoroalkoxyl chain can comprise a hydroxide (—OH), an amine, asulfhydryl (thiol) (—SH), a lactone, an amide, a carboxylic acid, and/orester functional group. It is understood that the straight or cyclicalkyl, alkoxyl, fluoroalkyl, and/or fluoroalkoxyl chain may compriseother suitable functional groups.

An exemplary sulfonamide is represented by the formula:

R14, R15, R16, R17, R18, R19, and/or R20 comprise a hydrogen, ahydroxide (OH), a halide, an aromatic carbon ring, a straight or cyclicalkyl chain, a straight or cyclic alkoxyl chain, a straight or cyclicfluoroalkyl chain, a straight or cyclic fluoroalkoxyl chain, othersuitable material, and/or combinations thereof. A chain contains fromabout 1 to about 8 carbon atoms. The straight or cyclic alkyl, alkoxyl,fluoroalkyl, and/or fluoroalkoxyl chain can comprise a hydroxide (—OH),an amine, a sulfhydryl (thiol) (—SH), a lactone, an amide, a carboxylicacid, and/or ester functional group. It is understood that the straightor cyclic alkyl, alkoxyl, fluoroalkyl, or fluoroalkoxyl chain maycomprise other suitable functional groups.

An exemplary lactam is represented by the formulas:

Alternatively, the exemplary lactam is represented by the formula

R21 and/or R22 comprise a hydrogen, a hydroxide (OH), a halide, anaromatic carbon ring, a straight or cyclic alkyl chain, a straight orcyclic alkoxyl chain, a straight or cyclic fluoroalkyl chain, a straightor cyclic fluoroalkoxyl chain, other suitable material, and/orcombinations thereof. A chain contains from about 1 to about 8 carbonatoms. The straight or cyclic alkyl, alkoxyl, fluoroalkyl, orfluoroalkoxyl chain can comprise a hydroxide (—OH), an amine, asulfhydryl (thiol) (—SH), a lactone, an amide, a carboxylic acid, and/orester functional group. It is understood that the straight or cyclicalkyl, alkoxyl, fluoroalkyl, or fluoroalkoxyl chain may comprise othersuitable functional groups. X is from about 2 to about 5.

The semiconductor device 200 is then moved to a lithography apparatusfor an exposing process. In the exposing process step 106, thephotosensitive layer 220 is exposed twice to an exposure energy such asdeep ultra-violet (DUV) through a photomask (mask or reticle) having apredefined pattern, resulting in a resist pattern that includes aplurality of exposed regions such as exposed features and a plurality ofunexposed regions. In one embodiment, the exposure beam used to exposethe photosensitive layer 220 includes extreme ultraviolet (EUV) exposureand/or electron-beam (e-beam) writing. Alternatively, the exposureprocess may utilize other exposure beams, such as ion beam, x-ray, deepultraviolet, and other proper exposure energy.

The patterned exposed and unexposed portions are formed by illuminatingmaterial layer with a exposure source through one or more photomasks (orreticles) to form an image pattern. The process may implement kryptonfluoride (KrF) excimer lasers, argon fluoride (ArF) excimer lasers, ArFimmersion lithography, ultraviolet (UV) exposure, extreme ultra-violet(EUV) exposure, and/or electron-beam (e-beam) writing.

In step 106, a double exposure patterning process is performed. Forexample, the photosensitive layer 220 is exposed to a first exposureenergy through a first mask 300 and then exposed to a second exposureenergy through a second mask 400. Referring to FIG. 3, the first maskwith a pattern 300 and second mask with a pattern 400 are components ofthe pattern 500 desired. The area designated by reference numeral 302 isexposed only once. The area designated by reference numerals 402 isexposed twice, during both the first and second exposures.

The nature of the PAGs and PBGs is such that the exposure energyresulting from a single exposure is sufficient to activate the PAGs inthe exposed areas to define a trench pattern. In one embodiment, theexposure energy resulting from double exposure is sufficient to activateboth the PAGs and the PBGs in the doubly exposed or overlapping areas(with the PAGs in those areas being activated by the first exposure andthe PAGs and PBGs being activated by the second exposure). As a result,in the doubly exposed areas, the PAGs and PBGs function to neutralizeone another such that, in one embodiment, upon development of thesubstrate 210, the effective result is as if the doubly exposed areashad not been exposed at all. The doubly exposed areas in one embodimentdefine a polymer that is insoluble during a developing process, whichcan be used to define a trench end-to-end pattern or other resistremaining pattern.

The intensities of the first and second exposure energies may beoptimized or adjusted to provide sharper contrast and resolution of thefinal pattern. In one embodiment, the second exposure energy is equal toor exceeds the threshold energy needed to activate the PAG and/or thePBG.

Referring to FIGS. 4 and 5, for purposes of example, it will be assumedthat the substrate 210 will be exposed first using the maskcorresponding to the pattern 300 and then exposed for a second timeusing the mask corresponding to the pattern 400. Using these conditions,FIG. 4 shows the exposure energy along line 305 applied to the firstmask with pattern 300 to activate the PAG. Similarly, FIG. 5 shows theexposure energy along line 405 applied to the second mask with pattern400 to activate the PAG and/or PBG. In the depicted embodiment, thefirst exposure energy is different than the second exposure energy. Thecombination of the two patterns 300,400 is illustrated as a pattern 500.

Referring to FIG. 6, a line 505 represents the cumulative exposureenergy resulting from the first and second exposures. FIG. 7 comparesthe original single exposure 605 with the double exposure 505. As can beseen, the final image contrast for the double exposure 505 is sharper,i.e., has a sharper slope 510, than the slope 610 for the singleexposure 605.

In one embodiment, which is illustrated in FIG. 8, after an exposureprocess, the base amount generated by the PBG is about equal to the acidgenerated by the PAG. Area 700 indicates the first exposure area, i.e.,areas in the photosensitive layer where the PAG is activated. Area 800indicates the second exposure area, i.e., areas in the photosensitivelayer where PAG and PBG are activated. Area 900 is exposed to both thefirst and second exposure energies to form a salt and therefore remainsafter a developing process. Areas 1000 are where acid has formed, andare washed away during a developing process to form a trench. In thiscase, because PAG and PBG quantum yield is almost the same, and thefirst exposure dosage equals the second, the area 1010 is an acid area,which can be removed by a developer solution.

In another embodiment, which is illustrated in FIG. 9, the base amountgenerated by the PBG is substantially greater than the acid generated bythe PAG. Area 700 indicates the first exposure area, i.e., areas in thephotosensitive layer where the PAG is activated. Area 800 indicates thesecond exposure area, i.e., areas in the photosensitive layer where PAGand PBG are activated. Area 900 is exposed to both the first and secondexposure energies to form a salt and therefore remains after adeveloping process. Areas 1000 are where acid has formed, and are washedaway during a developing process to form a trench. Areas 1010 remainafter a developing process because both PAG and PBG are activated, andthe amount of base generated by the PBG is more than enough toneutralize the acid generated by the PAG.

The amount of base generated depends on the initial PBG loading(concentration), conversion efficiency, the intensity of the exposureenergy, and/or mixing uniformity of the PBG with the other components ofthe photosensitive layer. The base depletes the acid and enhances thefinal acid distribution, providing an improved profile and tighterresolution.

It will be recognized that, although the embodiments described hereinemploy PAGs that are activated by an exposure energy lower than thatrequired to activate the PBGs, the opposite may be true, in which casethe exposure energy required to activate the PBGs is less than thatrequired to activate the PAGs.

Subsequently, the photoresist layer may be subjected to a post-exposurebake (PEB) process step 108. The coated photosensitive layer may bebaked in a step, referred to as pre baking process, to reduce thesolvent.

After a pattern exposure and/or post-exposure bake (PEB) process, thePAG in the photosensitive layer 220 (i.e., photoresist) may produce anacid and thus increase or decrease its solubility. The solubility may beincreased for positive tone resist (i.e., the acid will cleave an acidcleavable polymer, resulting in the polymer becoming more hydrophilic)and decreased for negative tone resist (i.e., the acid will catalyze anacid catalyzed crosslinkable polymer, resulting in the polymer becomingmore hydrophobic).

Similarly, after a pattern exposure and/or PEB process, the PBG in thephotoresist may produce a base that partially neutralizes or totallyneutralizes the acid. The base reacts with the acid to make the polymerless soluble to a developing solution.

The method proceeds to step 110, where the photosensitive layer isdeveloped by any suitable process to form a pattern in thephotosensitive layer. A developing solution may be utilized to removeportions of the photosensitive layer. An example of a developingsolution is tetramethylammonium hydroxide (TMAH). Any concentrationlevel of TMAH developer solution may be utilized, such as approximately2.38% TMAH developer solution. The developing solution may remove theexposed or unexposed portions depending on the resist type. For example,in the present example, the photosensitive layer 220 comprises anegative-type resist, so the exposed portions are not dissolved by thedeveloping solution and remain over substrate 210. If the photosensitivelayer 220 includes a positive-type resist, the exposed portions would bedissolved by the developing solution, leaving the unexposed portionsbehind. The semiconductor device may then be subjected to a rinsingprocess, such as a de-ionized (DI) water rinse. The rinsing process mayremove residue particles.

The remaining exposed portions (or unexposed portions) define a pattern.The pattern contains one or more openings or trenches, wherein portionsof the underlying substrate 210 are exposed. Subsequent processing mayinclude removing the exposed portions of the substrate 210 within theopenings. Alternatively, metal deposition, ion implantation, or otherprocesses can be carried out over the substrate 210. The patternedphotoresist may then be removed (or stripped) by any suitable process.For example, the patterned photoresist may be removed with a fluid (orstripping solution). The semiconductor device 200 may be subjected toone or more processes, such as additional patterning, etching,deposition, etc. processes, to form additional features of thesemiconductor device 200.

The present disclosure provides various methods and photosensitivematerials for lithography patterning. It should be understood that avariety of different patterns can be formed using the presentlydisclosed methods. By tuning the concentration of PAGs and PBGs,selecting the type of PAGs and PBGs, and/or adjusting the intensity ofthe exposure energies, trench end-to-end contrast may be improved, andtrench end-to-end critical dimensions reduced, simultaneously. Suchtuning provides better control over the overall acid and basedistribution that occurs during an exposure process. The basedistribution may be modified to enhance the final acid distribution,which provides improved acid/base distribution contrast, resulting in animproved pattern profile. The modified base distribution particularlyimproves resolution (contrast) of the resulting pattern. Moreover, thepresent methods are more cost efficient because they can extend existinglithography tools for use with smaller CDs.

Other variations in this spirit and scope are considered as consistentwith the present disclosure and are suggestive. For example, thelithography patterning methods can be used to pattern one material layerdisposed on a semiconductor wafer. This material layer can includesilicon, silicon oxide, silicon nitride, titanium nitride, siliconoxynitride, metal oxide (e.g. aluminum oxide or hafnium oxide), metalnitride, metal oxynitride, or siloxane. An additional material layer,such as bottom anti-reflective coating (BARC), may be formed on thesubstrate before forming the photosensitive layer(s). The photosensitivematerial can be positive tone or alternatively negative tone.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the detailed description thatfollows. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for forming a pattern on a substrate,the method comprising: providing a substrate; forming a photosensitivelayer over the substrate, wherein the photosensitive layer comprises apolymer that turns soluble to a developer solution, at least onephoto-acid generator (PAG), and at least one photo-base generator (PBG);exposing the photosensitive layer to a first exposure energy through afirst mask; after exposing to the first exposure energy, exposing thephotosensitive layer to a second exposure energy through a second mask,wherein a portion of the layer exposed to the second exposure energyoverlaps with a portion exposed to the first exposure energy; baking thephotosensitive layer; and developing the exposed photosensitive layer.2. The method of claim 1, wherein the first exposure energy issufficient to activate the PAG and/or the second exposure energy issufficient to activate the PAG and PBG.
 3. The method of claim 1,wherein the PAG is present at a first concentration, and the PBG ispresent at a second concentration.
 4. The method of claim 3, wherein thesecond concentration is greater than or equal to the firstconcentration.
 5. The method of claim 3, further comprising adjustingthe first concentration, second concentration, or both to improvecontrast and/or a critical dimension in the pattern.
 6. The method ofclaim 1, wherein the second concentration is greater than the firstconcentration and the portion of the photosensitive layer exposed to thesecond exposure energy remains after developing the exposedphotosensitive layer.
 7. The method of claim 1, wherein the secondconcentration is about equal to the first concentration and the portionof the photosensitive layer exposed to the second exposure energy iswashed away after developing the exposed photosensitive layer.
 8. Themethod of claim 1, wherein the second exposure energy is higher inintensity than the first exposure energy.
 9. The method of claim 1,further comprising adjusting an intensity of the first exposure energy,second exposure energy, or both to improve contrast and/or a criticaldimension in the pattern.
 10. The method of claim 1, wherein the PAGcomprises one or more sulfonium salts, iodinium salts,sulfonyldiazomethane compounds, N-sulfonyloxyimide compounds,benzoinsulfonate compounds, pyrogallol trisulfonate compounds,nitrobenzyl sulfonate compounds, sulfone compounds, and glyoximederivatives.
 11. The method of claim 1, wherein the PBG comprises one ormore of a carbamate, carbamonylhydroxyamine, oxime, sulfonamide, orlactam.
 12. A method for forming a pattern on a substrate, comprising:providing a substrate; forming a photosensitive layer on a substrate,the photosensitive layer comprising a polymer that turns soluble to adeveloper solution, a photo-acid generator (PAG) at a firstconcentration that decomposes to form acid in response to a firstexposure energy, and a photo-base generator (PBG) at a secondconcentration that decomposes to form a base in response to a secondexposure energy; exposing the photosensitive layer to the first exposureenergy through a first mask; after exposing to the first exposureenergy, exposing the photosensitive layer to the second exposure energythrough a second mask, wherein a portion of the layer exposed to thesecond exposure energy overlaps with a portion exposed to the firstexposure energy; baking the photosensitive layer; and developing theexposed photosensitive layer.
 13. The method of claim 12, wherein thesecond exposure energy is higher than the first exposure energy toactivate the PAG and PBG.
 14. The method of claim 12, further comprisingadjusting an intensity of the first exposure energy, second exposureenergy, or both to improve contrast and/or a critical dimension in thepattern.
 15. The method of claim 12, further comprising adjusting thefirst concentration, second concentration, or both to improve contrastand/or a critical dimension in the pattern.
 16. The method of claim 12,wherein the second concentration is greater than the first concentrationand the portion of the photosensitive layer exposed to the secondexposure energy remains after developing the exposed photosensitivelayer.
 17. The method of claim 12, wherein the second concentration isabout equal to the first concentration and the portion of thephotosensitive layer exposed to the second exposure energy is washedaway after developing the exposed photosensitive layer.
 18. A method forforming a pattern on a substrate, comprising: providing a substrate;forming a photosensitive layer on a substrate, the photosensitive layercomprising a polymer that turns soluble to a developer solution, aphoto-acid generator (PAG) at a first concentration that decomposes toform acid in response to a first exposure energy, and a photo-basegenerator (PBG) at a second concentration that decomposes to form a basein response to a second exposure energy; adjusting the firstconcentration, second concentration, or both to improve contrast and/ora critical dimension in the pattern; adjusting an intensity of the firstexposure energy, second exposure energy, or both to improve contrastand/or a critical dimension in the pattern; exposing the photosensitivelayer to the first exposure energy through a first mask; after exposingto the first exposure energy, exposing the photosensitive layer to thesecond exposure energy through a second mask, wherein a portion of thelayer exposed to the second exposure energy overlaps with the a portionexposed to the first exposure energy; baking the photosensitive layer;and developing the exposed photosensitive layer.
 19. The method of claim18, wherein the second exposure energy is sufficient to activate the PAGand PBG.
 20. The method of claim 18, wherein the second concentration isgreater than the first concentration and the portion of thephotosensitive layer exposed to the second exposure energy remains afterdeveloping the exposed photosensitive layer, or the second concentrationis about equal to the first concentration and the portion of thephotosensitive layer exposed to the second exposure energy is washedaway after developing the exposed photosensitive layer.